Written by Sigrid Blome-Eberwein, M.D. on August 30, 2019
To understand scars and laser treatments for scars, we need to understand skin, skin injury, and skin repair. Every injury to human skin deeper than the epidermal (top) layer (Diagram 1) leaves a scar after it heals.
The scar can be a slight difference in color or an obvious difference in the quality and surface of the scar compared to normal skin. This depends on the depth of the injury and elements left in the wound during the healing process. If the damage reaches deep into the dermal (second) layer of skin (Diagram 1), which has collagen, all glands, hair follicles, blood vessels, and nerve endings, skin grafting is usually performed to heal the open wound.
Skin grafting, a surgical procedure, involves taking skin from a non-injured area, most often the leg, and placing it on the open wound to close it. Most often, a split-thickness skin graft is used to heal burn wounds that will not heal alone. This type of skin graft involves only the upper layer of the skin with a little dermis attached. A full-thickness skin graft involves the entire thickness of skin. Full-thickness skin graft donor sites will not heal unless closed by suture; for that reason, they are limited to skin creases with extra skin.
After a skin grafting procedure or deep wound that healed slowly, scars can run the full spectrum in appearance—from flat and almost unnoticeable to red, raised, itchy, and tight. Scars can lack hair and nerve endings, or have irregular, ingrown hair and nerve endings. Scars from split-thickness grafting often show a mesh-pattern, which is caused by cutting little slits into the grafts so they can be stretched to cover a larger area during surgery.
Maturation, the process of scarring from wound healing to the end state of a scar, takes approximately five years. Right after wound healing, upon discharge from the hospital or clinic, scars are usually red, flat, and supple. Over the next three months, they often thicken and become raised, irritated, and itchy, as well as painful and tight. Sometimes this resolves over the next 6-18 months, sometimes only certain symptoms resolve, and sometimes all symptoms continue for a long time.
When discussing modern burn scar treatment and prevention, it is necessary to look at all aspects of scarring and treat each symptom separately. It is also important to understand that a scar will never turn back into normal skin, no matter how successful the treatment. For that reason, many physicians in the past suggested scar excision and/or replacement with nearby skin.
To eliminate “small” areas of scarring, plastic surgeons developed a variety of methods, including plain excision and closure, tissue expansion, local and distant flap coverage, microsurgical flap transfers, and (face) transplantation. While some of these procedures can result in good outcomes, many burn survivors suffer from scars that cannot be treated successfully with these methods because (1) their scars are in anatomically difficult locations, (2) they do not have enough healthy tissue available to transplant or (3) the skin of the transplant does not match the surrounding skin in color and consistency. If we compare the skin of our upper inner arm to the skin of our hand or the skin of our lower leg, we will notice these areas look totally different. It should, therefore, be obvious that we cannot simply replace one area of skin with another.
Scar prevention begins in the operating room with the skin chosen as a donor site. If we transplant skin from the thigh to the nose, a color difference is pre-programmed. But even when there is enough healthy skin available to carefully match our donor site to the recipient site skin, it will heal by scarring. The result will always be a scar, not normal skin. And even under the most fortunate circumstances—that there is enough healthy skin surrounding the scar so we can simply excise it (cut it out) and close the cut—this cut will also leave a scar.
All this to say that, in “modern” scar treatment, we talk about “scar rehabilitation” as opposed to “scar reconstruction.” The word “rehabilitation” implies that we try to make the scar as close to normal skin as possible, knowing that we will not “get rid of it.”
Unpleasant scar developments are most prominent in teenagers and young adults, but any age group can have severe scar changes, depending on the skin type. The darker the skin, the more severe the scarring. Each scar symptom has different causes and treatment options, but standard for any modern scar treatment and prevention program should be moisturizer, scar massage, stretching, splinting at night, and compression with or without silicone inserts.
In recent years, laser scar treatment has gained widespread interest and use. Experimental studies have found that certain laser applications can actually make scars better after they have fully matured (after years) and also in the more acute scar remodeling phase (the first 3-18 months.)
Laser treatments have been used successfully for years to alleviate the itching and redness in scars (ref 1, 2). More recently, non-ablative and ablative CO2 lasers have been used to decrease scar thickness and improve surface irregularity, tightness, and overall structure of the scar (ref 3, 4). Other lasers can be used to treat ingrown hair or hair from skin grafts in areas where there should be no hair (nose, palm of hands, neck, etc.) and, with limited success, color difference of scars.
Simplified, a laser is a technique to bundle and filter out certain wavelengths of light and direct them very specifically. The exact mechanism of action on scars depends on the color and energy of the light. All lasers act by “burning,” which seems counterintuitive in burn scars. However, by burning certain elements in the scar specifically, we can stimulate the body to start a repair process. The result of that process looks more like normal skin. In a pigment laser, for example, the light is absorbed by the pigment in the scar or skin. It destroys the pigment and the body’s own cells, transports the debris away and disposes of it through the liver or kidney. A hair removal laser burns the hair follicle cells: the hair falls out and does not grow back.
Non-ablative resurfacing lasers bundle the light energy underneath the epidermis (top layer of skin) and cause a blister-like reaction, which stimulates repair mechanisms in the skin.
The ablative CO2 lasers bundle the light energy at various depths throughout the entire skin (and more), so they cause a controlled level burn. In wrinkle treatment, these lasers essentially cause a second-degree burn, which heals with a “scar” that is tighter and smoother than surrounding skin. In scars, though, there are not enough elements left in the skin to heal that new burn wound. An open wound would result in more scarring—obviously not the desired effect.
Fractional treatment, a new development, has made these lasers interesting for scar treatment. Fractional means that only small holes are burnt into the surface and tissue, which remain surrounded by uninjured tissue. The holes stimulate a repair mechanism that improves the scar in the long run.
At this point, nobody knows exactly how this is possible, but it works. Several scientific studies have proven that treatment with the fractional CO2 laser improves burn scar thickness, tightness, and sensation, as well as overall appearance and feel (ref 3, 4). The holes can also be used to deliver certain drugs (e.g., steroids and bleaching creams) into the scar evenly. At present, researchers are exploring this modality.
While we started out treating only matured scars—scars over one year old—the benefits from treating scars still in the remodeling phase (Diagram 2) and getting worse are becoming more and more obvious.
Scars mature faster and do not become as hypertrophic if they are treated with the fractional CO2 laser in this phase. The standard scar treatment is also continued during this phase (see above). However, the wound should be completely healed and, in general, scars under three months old are too fragile to undergo the treatment.
We are currently treating all age groups, as long as they can sit still for the procedure or tolerate anesthesia. In general, most burn survivors have larger areas that need treatment and prefer anesthesia. Even with topical numbing cream and pain medicine, treatment with the CO2 laser is painful.
If it is a small area or the scar is completely numb (no nerve endings), treatment can be done in awake adults. Children are sedated because they cannot be counted on to sit still. The laser can cause severe damage if a patient moves during treatment.
Scars in development (3-12 weeks post wound-healing) can be treated with non-ablative lasers to relieve itching and prevent some of the thickening of the scars. Intense pulsed light (IPL) treatments may also eliminate some redness and itch.
At 3-6 months post wound-healing, fractional CO2 laser treatments can begin on thickening, hyperactive scars. The treatments need to be at least eight weeks apart to let the scar recover and remodel between treatments. The fractional CO2 laser treatments speed the process of scar maturation and prevent some of the collagen deposition that makes scars thick and tight.
After scar maturation (12-18 months after wound healing), scars are treated according to symptoms. The fractional CO2 laser is effective for scar hypertrophy (thickness), tightness, and surface irregularities. Pigment laser treatments may help with hyperpigmentation (darker spots), and hair removal laser treatments may be used to eliminate ingrown hairs and hair growth from skin grafts. IPL treatments may be used for the more superficial dark spots that sometimes develop in skin-grafted scars. A combination of scar injection with steroids and laser treatments is possible in some cases.
In theory, there is no endpoint for laser treatments. Even very old, mature scars respond favorably to fractional CO2 laser treatments. Because there are no reports of someone receiving too many laser treatments for scars, this is a difficult question to answer. There is significant discomfort and cost associated with laser treatments, so most centers treat scars 3 -10 times with a laser. Most burn survivors in our center choose to discontinue treatments when they no longer notice a significant improvement—between 3 and 8 treatments. That number does not take into consideration that additional hair and pigment treatments may be requested.
The Phoenix Society and most American Burn Association-accredited Burn Centers can refer you to someone experienced in laser treatment of burn scars. Many dermatologists perform laser procedures on the skin, but it is important to make sure that whomever you go to has experience treating burn scars, which respond differently to treatments than normal skin. Most dermatologist offices will not have the capability to perform these procedures under sedation. In addition, the Burn Prevention Network website (ref 5) offers a question-and-answer forum regarding laser treatments specific to scars.
Sigrid Blome-Eberwein, M.D., is the Associate Director of the Leigh Valley Health Network Regional Burn Center in Allentown, PA, and Associate Professor at the University of South Florida Department of Surgery. She is a member of the Phoenix Society for Burn Survivors, American Burn Association, American Plastic Surgery Association, American Laser Medicine Society, German Plastic Surgery Society, and the German Surgery Association. Blome-Eberwein has worked in burn care and reconstruction since 1995, and completed a Fellowship in Burn Surgery at University of Southern California.
Sheridan RL, MacMillan K, Donelan M, Choucair R, Grevelink J, Petras L, Lydon M, Tompkins R. Tunable dye laser neovessel ablation as an adjunct to the management of hypertrophic scarring in burned children: pilot trial to establish safety. J Burn Care Rehabil. 1997;18(4):317-320.
Parrett BM, Donelan MB. Pulsed dye laser in burn scars: current concepts and future directions. Burns. 2010;36(4):443-449. doi: 10.1016/j.burns.2009.08.015.
Blome-Eberwein S, Gogal C, Weiss MJ, Boorse D, Pagella P. Prospective Evaluation of Fractional CO2 Laser Treatment of Mature Burn Scars. J Burn Care Res. 2016;37(6):379-387.
Hultman CS, Friedstat JS, Edkins RE, Cairns BA, Meyer AA. Laser resurfacing and remodeling of hypertrophic burn scars: the results of a large, prospective, before-after cohort study, with long-term follow-up. Ann Surg. 2014;260(3):519-529.
Burn Prevention Network. Scar research: a research fund devoted to serious scars and the survivors. Retrieved from http://www.myscarresearch.com.